Genetic Basis of Anorexia Uncovered

Scientists have identified genetic changes that may increase the risk of developing the eating disorder anorexia, according to a new study.

The variations include both small changes at single points within gene sequences, as well as large segments of DNA that have been duplicated or deleted.

The study is the largest to look for such genetic associations with anorexia.

However, the researchers said that while these genetic variations are promising leads, future studies with even more participants are needed to confirm the findings, as well as to tease out more such genetic markers for anorexia.

Once a significant number of genes are found, "you have the ability to do a diagnostic from the genetic markers for people who are at risk," said study researcher Dr. Hakon Hakonarson, director of the Center for Applied Genomics at The Children’s Hospital of Philadelphia.

The results were published in the Nov. 16 issue of the journal Molecular Psychiatry.

Anorexia genes

Patients with anorexia nervosa have an irrational fear of gaining weight and a distorted perception of their body image. About 0.9 percent of women in the United States have been diagnosed with the eating disorder. The condition affects 10 times as many women as it does men, and often begins during adolescence.

Studies done on twins have led researchers to believe that anorexia is highly heritable, and that genes could account for more than half of a person's susceptibility to the condition. However, few genes have been implicated as risk factors, the genetic underpinnings of anorexia have remained, for the most part, unknown.

To solve the mystery, Hakonarson and his colleagues scanned the genomes of 1,003 people with anorexia (whose average age was 27), and compared them with the genomes of 3,733 children (whose average age was 13) who did not have anorexia. While it's possible that some of the children might later develop anorexia, the number would be so small that it would be unlikely to impact the analysis, Hakonarson said.

The researchers found a few spots along the genome where the two groups differed. These so-called single-nucleotide polymorphisms, or SNPs could play a role in the genetic underpinnings of the disease.

One such spot was in a gene called OPRD1, which previous studies had suggested was linked to anorexia, and the new study validated the result. Another spot was between two genes called CHD10 and CHD9. Previous research by Hakonarson and colleagues linked this particular genetic region with autism, and the genes are thought to influence how brain cells talk to each other.

"The fact that they come up now in this disease, which is another sort of neural psychiatric disease, is in my view, very intriguing," Hakonarson told MyHealthNewsDaily. Although the diseases' symptoms are different — autism involves distortions in social interactions while anorexia involves distortions of body image — the brain pathways that are disrupted in the two conditions could be similar, he said.

Duplications and deletions

The researchers also looked for genetic changes called copy number variants, or CNVs, which are chunks of DNA that are replicated or missing. The study was the first to look for such variations in people with anorexia. Patients with some psychiatric conditions, such as schizophrenia and autism, have a greater number of certain CNVs.

However, anorexia patients did not have a greater number of the CNVs linked to other diseases, and the researchers suspect these particular genetic variations do not play a role in the eating disorder as they do in other psychiatric illnesses.

However, a few other CNVs showed up in anorexia patients, albeit in a small number of patients. One such CNV was a deletion on chromosome 13. This CNV occurred 10 times more frequently in those with anorexia than among those without the condition.

The researchers now plan to scan the genomes of the people with anorexia again, looking for the chromosome 13 deletion and other CNVs unique to anorexia, Hakonarson said. It's possible that more patients have these CNVs, but they were missed in the original analysis because they differed slightly from the types of genetic changes the researchers were looking for.